Desenvolvimento de bionanocomp��sitos: nano e microcristais de celulose com poli (��lcool vin��lico) e poli (��cido l��tico)

This work has the main objective to obtain nano and microcrystals of cellulose, extracted from the pineapple leaf fibres (PALF), as reinforcement for the manufacture of biocomposite films with polymeric matrices of Poly(vinyl alcohol) (PVA) and Poly(lactic acid) (PLA). The polymer matrices and the nano and microcrystals of cellulose were characterised by means of TGA, FTIR and DSC. The analysis was performed on the pineapple leaves to identify the macro and micronutrients. The fibers of the leaves of the pineapple were extracted in a desfibradeira mechanical. The PALF extracted were washed to remove washable impurities and subsequently treated with sodium hydroxide (NaOH) and sodium hypochlorite (NaClO) in the removal of impurities, such as fat, grease, pectates, pectin and lignin. The processed PALF fibers were hydrolysed in sulfuric acid (H2SO4) at a concentration of 13.5 %, to obtain nano and microcrystals of cellulose. In the manufacture of biocomposite films, concentrations of cellulose, 0 %, 1 %, 3 %, 6 %, 9% and 12% were used as reinforcement to the matrices of PVA and PLA. The PVA was dissolved in distilled water at 80 �� 5 oC and the PLA was dissolved in dichloromethane at room temperature. The manufacture of biocomp��sitos in the form of films was carried out by "casting". Tests were carried out to study the water absorption by the films and mechanical test of resistance to traction according to ASTM D638-10 with a velocity of 50 mm/min.. Chi-square statistical test was used to check for the existence of significant differences in the level of 0.05: the lengths of the PALF, lengths of the nano and microcrystals of cellulose and the procedures used for the filtration using filter syringe of 0.2 ��m or filtration and centrifugation. The hydrophilicity of biocomp��sitos was analysed by measuring the contact angle and the thickness of biocomp��sitos were compared as well as the results of tests of traction. Statistical T test - Student was also applied with the significance level (0.05). In biodegradation, Sturm test of standard D5209 was used. Nano and microcrystals of cellulose with lengths ranging from 7.33 nm to 186.17 nm were found. The PVA films showed average thicknesses of 0.153 ��m and PLA 0.210 ��m. There is a strong linear correlation directly proportional between the traction of the films of PVA and the concentration of cellulose in the films (composite) (0,7336), while the thickness of the film was correlated in 0.1404. Nano and microcrystals of cellulose and thickness together, correlated to 0.8740. While the correlation between the cellulose content and tensile strength was weak and inversely proportional (- 0,0057) and thickness in -0.2602, totaling -0,2659 in PLA films. This can be attributed to the nano and microcrystals of cellulose not fully adsorbed to the PLA matrix. In the comparison of the results of the traction of the two polymer matrices, the nano and microcrystals have helped in reducing the traction of the films (composite) of PLA. There was still the degradation of the film of PVA, within a period of 20 days, which was not seen in the PLA film, on the other hand, the observations made in the literature, the average time to start the degradation is above 60 days. What can be said that the films are biodegradable composites, with hydrophilicity and the nano and microcrystals of cellulose, contribute positively in the improvement of the results of polymer matrices used.

Biphasic composite of Tricalcium phosphate reinforced with Hydroxyapatite Whiskers

Biphasic calcium phosphates have received considerable attention due to their optimum dissolution rate in the human body after implantation. These materials are composed of hydroxyapatite (HA) and resorbable tricalcium phosphate (TCP). In the present investigation, HA whiskers are reinforced into TCP to enhance the mechanical properties of this biphasic composite. Various amounts (30-50 wt%) HA whiskers are reinforced in TCP matrix. Microstructural characterization has been carried out using field-emission scanning electron microscope. Mechanical properties have been investigated by microindentation in a universal testing machine (UTM). As TCP is resorbable, it will dissolve in body fluid and there is a strong possibility for the faceted HA whiskers to interact with functional groups present in the body fluid surroundings.

Manipulating Crystallographic Texture of Sn Coatings by Optimization of Electrodeposition Process Conditions to Suppress Growth of Whiskers

The effects of two major electrodeposition process conditions, electrolyte bath temperature and current density, on the microstructure and crystallographic texture of pure tin coatings on brass and, ultimately, on the extent of whisker formation have been examined. The grain size of the deposited coatings increased with increasing electrolyte bath temperature and current density, which significantly affected the dominant texture: (211) or (420) was the dominant texture at low current densities whereas, depending on deposition temperature, (200) or (220) became the dominant texture at high current densities. After deposition, coatings were subjected to different environmental conditions, for example isothermal aging (room temperature, 50A degrees C, or 150A degrees C) for up to 90 days and thermal cycling between -25A degrees C and 85A degrees C for 100 cycles, and whisker growth was studied. The Sn coatings with low Miller index planes, for example (200) and (220), and with moderate aging temperature were more prone to whiskering than coating with high Miller index planes, for example (420), and high aging temperature. A processing route involving the optimum combination of current density and deposition temperature is proposed for suppressing whisker growth.

Raman scattering of non-planar graphite: arched edges, polyhedral crystals, whiskers and cones

Planar graphite has been extensively studied by Raman scattering for years. A comparative Raman study of several different and less common non-planar graphitic materials is given here. New kinds of graphite whiskers and tubular graphite cones (synthetic and natural) have been introduced. Raman spectroscopy has been applied to the characterization of natural graphite crystal edge planes, an individual graphite whisker graphite polyhedral crystals and tubular graphite cones. Almost all of the observed Raman modes were assigned according to the selection rules and the double-resonance Raman mechanism. The polarization properties related to the structural features, the line shape of the first-order dispersive mode and its combination modes, the frequency variation of some modes in different carbon materials and other unique Raman spectral features are discussed here in detail.

Uso de res��duos da fabrica����o de celulose e papel e da reciclagem de papel.

2010

Metodologias de tratamento em microfilmes de acetato de celulose

A presente disserta����o, integra-se no projeto ���Digitaliza����o e Tratamento da Filmoteca Ultramarina Portuguesa���, que inclui o tratamento e digitaliza����o de uma cole����o de microfilmes em pel��culas de 35 mm em AC. A cole����o �� composta por mais de meio milh��o de exposi����es (511.397) de variadas marcas comerciais. Deste conjunto, os negativos da marca Perutz s��o a parte considerada em pior estado de preserva����o, contendo itens considerados irrecuper��veis, devido ao seu total encurvamento e enrolamento, comportamento incomum relacionado com a deteriora����o do AC. Portanto, este conjunto constitui o nosso objeto de estudo, priorit��rio a recuperar a informa����o contida nestes microfilmes, pois as cole����es originais, em papel, est��o inacess��veis e em mau estado de conserva����o. Devido a uma deteriora����o at��pica, uma das etapas principais �� compreender o material, tendo-se recorrido �� MO, para an��lise da estratigrafia, �� ��-FTIR e �� medi����o da acidez com as A-D STRIPS�� e dois m��todos de potenciometria de pH (com a utiliza����o de dois tipos de el��trodo, superf��cie plana e microel��trodo). Nos microfilmes aparentemente imposs��veis de desenrolar, foram ensaiados e comparados neste estudo, diferentes tratamentos de C&R tradicionalmente aplicados nesta ��rea, designadamente humidifica����o e transfer��ncia de emuls��o, os quais se revelaram inadequados para as deteriora����es em presen��a. Foi assim necess��rio recorrer a outras ��reas afins da fotografia, para poder encontrar uma solu����o j�� testada com sucesso, a qual estaria na ��rea do cinema, com o tratamento deshrinking que permitiu a recupera����o da imagem possibilitando a sua informatiza����o e coloca����o em base de dados, com o benef��cio inesperado de uma planifica����o permanente do objeto. Recorreu-se tamb��m �� ��rea da digitaliza����o 3D e modula����o computacional, mas sem resultados at�� a data. Assim, o tratamento deshrinking mostrou-se o mais eficaz sendo aprimorado, tendo-se passado de uma simples a����o pontual e revers��vel de planifica����o para uma mais definitiva.

Transformation of maize using silicon carbide whiskers

As the most commercially valuable cereal grown worldwide and the best-characterized in genetic terms, maize was predictably the first target for transformation among the important crops. Indeed, the first attempt at transformation of any plant was conducted on maize (1). These early efforts, however, were inevitably unsuccessful, since at that time, there were no reliable methods to permit the introduction of DNA into a cell, the expression of that DNA, and the identification of progeny derived from such a ���transgenic��� cell (2). Almost 20 years later, these technologies were finally combined, and the first transgenic cereals were produced. In the last few years, methods have become increasingly efficient, and transgenic maize has now been produced from protoplasts as well as from Agrobacterium-medieited or ���Biolistic��� delivery to embryogenic tissue (for a general comparison of methods used for maize, the reader is referred to a recent review���ref. 3). The present chapter will describe probably the simplest of the available procedures, namely the delivery of DNA to the recipient cells by vortexing them in the presence of silicon carbide (SiC) whiskers (this name will be used in preference to the term ���fiber,��� since it more correctly describes the single crystal nature of the material).

Extraction of cellulose whiskers from cassava bagasse and their applications as reinforcing agent in natural rubber

In this work cassava bagasse, a by-product of cassava starch industrialization was investigated as a new raw material to extract cellulose whiskers. This by-product is basically constituted of cellulose fibers (17.5 wt%) and residual starch (82 wt%). Therefore, this residue contains both natural fibers and a considerable quantity of starch and this composition suggests the possibility of using cassava bagasse to prepare both starch nanocrystals and cellulose whiskers. In this way, the preparation of cellulose whiskers was investigated employing conditions of sulfuric acid hydrolysis treatment found in the literature. The ensuing materials were characterized by transmission electron microscopy (TEM) and X-ray diffraction experiments. The results showed that high aspect ratio cellulose whiskers were successfully obtained. The reinforcing capability of cellulose whiskers extracted from cassava bagasse was investigated using natural rubber as matrix. High mechanical properties were observed from dynamic mechanical analysis. (C) 2010 Elsevier B.V. All rights reserved.

Extrusion and characterization of functionalized cellulose whiskers reinforced polyethylene nanocomposites

The surface of ramie cellulose whiskers has been chemically modified by grafting organic acid chlorides presenting different lengths of the aliphatic chain by an esterification reaction. The occurrence of the chemical modification was evaluated by FTIR and X-ray photoelectron spectroscopies, elemental analysis and contact angle measurements. The crystallinity of the particles was not altered by the chain grafting, but it was shown that covalently grafted chains were able to crystallize at the cellulose surface when using C18. Both unmodified and functionalized nanoparticles were extruded with low density polyethylene to prepare nanocomposite materials. The homogeneity of the ensuing nanocomposites was found to increase with the length of the grafted chains. The thermomechanical properties of processed nanocomposites were studied by differential scanning calorimetry (DSC), dynamical mechanical analysis (DMA) and tensile tests. A significant improvement in terms of elongation at break was observed when sufficiently long chains were grafted on the surface of the nanoparticles. It was ascribed to improved dispersion of the nanoparticles within the LDPE matrix. (C) 2009 Elsevier Ltd. All rights reserved.

Tratamento do efluente alcalino do branqueamento da polpa de celulose pelo processo de separa����o por membranas

O presente trabalho estuda o reaproveitamento do efluente alcalino do branqueamento da polpa, da ind��stria de celulose, atrav��s de processos de separa����o com membranas. Para tanto, foram realizados testes com o efluente industrial para diferentes membranas e, simultaneamente, foi pesquisada a aplica����o do processo de flota����o como pr��-tratamento para retirada de fibras do efluente. A avalia����o dos resultados foi realizada por meio de determina����es anal��ticas e monitoramento de alguns par��metros. Os experimentos foram executados em equipamentos de bancada e piloto. A etapa de separa����o com membranas envolveu os processos de ultrafiltra����o, nanofiltra����o, osmose reversa e combina����es destas opera����es. De forma a escolher um processo com reten����o e fluxo permeado adequados variou-se durante os testes a press��o atrav��s das membranas e a temperatura. As an��lises realizadas para a caracteriza����o do efluente foram: pH, condutividade el��trica, turbidez, s��lidos totais (ST), demanda qu��mica de oxig��nio (DQO), compostos organo-halogenados (AOX), ferro, magn��sio, c��lcio, s��dio, pot��ssio e mangan��s. A DQO foi o principal crit��rio utilizado para avaliar a qualidade do permeado. Os ensaios de flota����o foram realizados com e sem adi����o de compostos qu��micos auxiliares. A efici��ncia do processo foi avaliada atrav��s das an��lises de ST, condutividade el��trica, pH, recupera����o de fibras, teor de alum��nio, turbidez e visualmente Os resultados indicaram que todos os processos testados trouxeram uma melhoria nas caracter��sticas do efluente, incluindo redu����es de at�� 90% no valor de DQO em alguns casos. O processo que apresentou a melhor performance foi a combina����o UF5+ORP. A investiga����o preliminar sobre a flota����o das fibras mostrou que, apesar de ter atingido uma remo����o de fibras de 95% ainda havia a presen��a de part��culas grosseiras, as quais poderiam causar danos aos processos com membranas. Mais estudos devem ser realizados no sentido de otimizar o processo de flota����o.

Estudo da agrega����o de surfactantes ani��nicos em presen��a de (hidroxipropil)celulose

As t��cnicas de espectrofluorimetria, viscosimetria e espalhamento de luz t��m sido utilizadas no estudo da agrega����o de diferentes surfactantes ani��nicos em presen��a de 0,5% (m/v) de (hidroxipropil)celulose, no regime dilu��do (HPC Mw = 173000 g/mol), e em moderada for��a i��nica (NaCl 0,1 M). Admitindo-se uma faixa geral de concentra����o, entre 10-5 e 10-2 mol.L-1, foram empregados neste estudo os surfactantes colato de s��dio (CS), deoxicolato de s��dio (DC), derivados dos sais bilares, e o alquilsint��tico dodecil sulfato de s��dio (SDS). O pol��mero HPC contribui diferentemente no processo de agrega����o de cada surfactante, evidenciado pela mudan��a dos valores da concentra����o de agrega����o cr��tica, C1, em rela����o �� concentra����o micelar cr��tica (cmc), obtidos pela t��cnica de espectrofluorimetria. Ambos os valores de C1 diminuem com respeito �� cmc para SDS, bem como para DC, enquanto um ligeiro aumento �� observado para CS. Os dados de viscosidade relativa, ��rel, indicam um aumento substancial da viscosidade dos sistemas HPC/sais biliares a altas concentra����es de surfactante. Diferentemente, para o sistema HPC/SDS, os valores de ��rel passam por um m��ximo a 3 mmol.L-1 em agregados e decresce a valores abaixo da viscosidade da solu����o polim��rica livre de surfactante. As medidas da temperatura de turbidez (Tturb), por espalhamento de luz, para os sistemas HPC/sais biliares, mostraram um crescimento gradual de Tturb em fun����o do aumento da concentra����o de surfactante, de 37 oC (0,5% HPC/NaCl 0,1 M) at�� estabilizar-se em torno de 50o C, para concentra����es mais elevadas. Por outro lado, para HPC/SDS, a Tturb cresce acentuadamente, superando a temperatura de 100 oC a contra����es maiores do que 20 mmol.L-1. Atrav��s do espalhamento de luz din��mico, verificou-se a exist��ncia de dois modos difusivos (r��pido e lento) para todos os sistemas estudados. A principal contribui����o �� proveniente do modo r��pido, exceto na faixa de concentra����o entre C1 e a concentra����o de satura����o, C2, na qual ambos os modos contribuem igualmente. Esses modos est��o relacionados inicialmente a agregados HPC/surfactante e a ���clusters��� do pol��mero e, posteriormente, a agregados HPC/surfactante e micelas livres. Os resultados indicam uma intera����o HPC/SDS mais efetiva do que HPC/DC ou HPC/CS, fato este relacionado �� estrutura dos agregados formados. Comparativamente, os agregados HPC/sais biliares s��o menores, possuem menor densidade de carga e s��o mais r��gidos do que os agregados de HPC/SDS.

Utiliza����o de res��duos alcalinos de ind��strias de celulose na corre����o da acidez do solo

O descarte no solo �� uma alternativa vi��vel de disposi����o final e aproveitamento agr��cola de v��rios res��duos industriais. Com o objetivo geral de avaliar os efeitos do res��duo alcalino ���dregs+grits��� (DG) como corretivo de acidez e em atributos de solo, plantas e ��gua de percola����o, foram conduzidos dois experimentos em vasos, a c��u aberto. No primeiro experimento, em vasos de 2 L de um Latossolo Vermelho distr��fico (camada de 0-20 cm), avaliaram-se as fra����es granulom��tricas do DG (< 0,30; 0,30-0,84; 0,84���2,00; >2,00 mm) e o DG integral, em doses baseadas no valor de neutraliza����o (VN); DG integral com base no ��ndice PRNT; mistura de CaCO3+MgCO3 e testemunha sem corre����o. No segundo experimento, em colunas de PVC, contendo as camadas de 0-20 e 20-50 cm de tr��s solos (Latossolo Vermelho distr��fico, Argissolo Vermelho distr��fico ar��nico e Argissolo Vermelho distr��fico t��pico), foram avaliadas doses de DG de 0, 0,5; 1,0 e 2,0 vezes a necessidade de calagem para atingir pH 6,0 para cada solo, al��m de CaCO3+MgCO3 e dose DG 1,0 sem aduba����o. No primeiro experimento, ap��s 180 dias, todas as fra����es proporcionaram valores de pH superiores a 6,0, com rea����o mais r��pida das fra����es mais finas e maior efeito residual das fra����es mais grossas. O ��ndice PRNT se mostrou inadequado para defini����o de doses do res��duo, sendo o VN mais apropriado No segundo experimento, os efeitos imediatos e residuais sobre atributos relacionados �� acidez do solo, avaliados at�� 240 dias, aumentaram com as doses do res��duo, com resposta dependente do tipo de solo. A concentra����o de Na+, mesmo com a dose 2,0 DG, n��o afetou a estrutura f��sica dos solos, enquanto os teores de metais pesados no solo, plantas e ��guas de percola����o n��o apresentaram diferen��as entre os tratamentos. O res��duo DG pode ser usado como corretivo de acidez do solo, n��o apresentando efeitos significativos em atributos de solo, planta e ��gua relacionados �� qualidade ambiental.